Nonferrous metal



Patented Nov. 17, 1936 lTED STATES PATENT OFFICE NONFERROUS METAL NoDrawing. Application September 12, 1935,

Serial No. 40,342. 21, 1933 2 Claims.

This application is a continuation in part of our application Serial No.752,184.

The invention relates to improvements in zinc alloys and to articlesmade therefrom such as 5 rolled sheets.

It is known to prepare binary alloys of zinc for special purposes.Moreover, good quality commercial brands of zinc, which contain lead andperhaps certain other elements such as cadmium are commonly used for themanufacture of engraving sheets. It is known that zinc in its cast statehas a crystalline structure which makes it difficult to work and untilsuch structure has been modified by heat treatment or other means, it isunsuitable for many industrial purposes. Further, zinc both in the purestate and also when mixed or alloyed with certain other elements such aslead can be rolled successfully only at temperatures not exceeding 200C., and 20 after rolling either hot or cold it undergoes seriousincrease of grain size when heated to temperatures of 250 to 300 C.

According to the present invention alloys of zinc are prepared whichcontain at least 99% of zinc, and nickel and/or cobalt together withsilicon in an amount not greater than is required to form a silicide.The proportion of the metallic element or elements is usually from 0.02to 0.25 per cent (preferably 0.10 to 0.18 per cent) and that of siliconfrom 0.001 per cent upwards (preferably 0.001 to 0.03 per cent),provided that the ratio of silicon to the metallic element or elementsmust not exceed that corresponding to the chemical composition of thesilicide or silicides of the particular element or'elements, but may beconsiderably less than this amount. The proportions are those in thefinished alloy as some of the added ingredients may be lost in thedross. The purpose of the silicon is largely to act as a deoxidant andthis purpose is fulfilled if the alloy contains any amount of residualsilicon which is analytically detectable.

Small quantities of other elements may be present, notably lead (say 0.1or 0.3%) which improves the etching and cutting properties of engravingsheets.

A deficiency of nickel may be met to some extent by an addition of lead;a preferred proportion of nickel is in the neighbourhood of 0.1 to 0.15per cent with, say, 0.1 per cent of lead.

A suitable method of incorporating the ingredients is as followsz- Thenickel and silicon are first alloyed to contain a suitable proportion ofsilicon, that is, not more than 20% of silicon and not less than 80% InGreat Britain October of nickel. After alloying this metal is subdividedbypouring in a thin stream into water in the usual way. A proportion ofthis alloy is dissolved in molten zinc to make an alloy containing about5% of nickel with a corresponding percentage of silicon. This rich alloyis used by adding to the molten zinc to give the proportion of nickelrequired in the casting, which is then ready for the hot rollingoperation.

Alloys prepared according to the present invention possess veryfavourable qualities as compared with zinc itself or with the previouslyknown alloys of zinc. Thus the new ternary alloys of zinc, nickel, andsilicon cast well; they are readily worked hot, from temperatures of 350C. or even higher, and are capable of undergoing severe cold working.The grain size after hot and/or cold working is not seriously increasedby heating at temperatures as high as 350 to 380 C. The alloys possessboth in the cast and in the worked state great ductility and a hardnesswhich makes them suitable for many technical applications. As a resultof these valuable properties the alloys are capable of being rolleddirect from the cast ingots without preliminary heat-treatment, and atmuch higher temperatures than are customary with zinc or the usualalloys of zinc, and their high ductility enables them to be rolled intothin sheet strip or foil and to be drawn into wire. In fact, thepresence of a small proportion of a metal silicide greatly assistsmechanical working of the zinc alloy, in general.

The alloys possess numerous technical applications and they areparticularly suitable, for example, for the manufacture of engravingsheets. Such engraving sheets are characterized by exceptionalcleanliness, uniformity, and rapidity of etching, while their immunityfrom any development of a grain structure at temperatures encounteredduring the burning-in process considerably simplifies the latteroperation. Sheets for use in lithography afford another illustration oftheir successful application in the arts. The alloys are alsoparticularly suitable for extruding into rods or rolling and drawinginto wire.

The zinc employed in the preparation of these alloys may be electrolyticzinc or commercial zinc; in general the former is preferred. In additionto the elements already enumerated, that is in addition to one or moreof the metallic elements previously named and to the correspondingproportion of silicon, the alloys may contain, if desired for specialreasons, small amounts of other elements such as aluminium or cadmium orlead.

A typical alloy which may be prepared according to the present inventioncontains 0.13 per cent of nickel, 0.01 per cent of silicon and 0.1 percent of lead. The alloying elements may be added to the molten zincbefore casting, but it is preferable to prepare initially an alloy ofzinc, nickel, and silicon which is relatively rich in nickel and siliconand then incorporate this in the zinc. It has been found that the alloysare best prepared by melting in an electric induction furnace.

The function of the silicon appears to be twofold; it appears to efiectcomplete deoxidation of the alloy and so to allow of the production ofsound dense castings free from porosity and from oxide inclusions; it isfurther believed that the residual silicon may be present in the form of2,

metallic silicide such as NizSl or CozSi etc., and that it may exist inthis combination as a disperse phase distributed throughout the mass ofthe alloy.

We declare that what we claim is:-

1. An alloy for engraving sheets capable of hot working fromtemperatures exceeding 350 C. and capable of reheating thereto withoutincrease of grain size, containing 0.02% to 0.25% of a metal selectedfrom the group consisting of nickel and cobalt, 0.001% to 0.03% ofsilicon, substantially 0.10% to 0.30% of lead, and the remaindercompletely deoxidized zinc.

2. An alloy as in claim 1, in which the content of nickel is 0.13%.

HENRY CHARLES ANSTEY. WILLIAM ERNEST ALKINS.

